1. Field of the Invention
The invention relates to a process for making alkoxylates of narrow molecular weight distribution. More particularly, the invention relates to a process for alkoxylation in the presence of a catalyst of rare earth triflimides.
2. Background of the Invention
Nonionic Surfactants are industrially manufactured by reaction of a organic compound with ethylene oxide using a base as catalyst e.g. sodium or potassium hydroxide. Nonionic surfactants are commonly manufactured from the ethoxylation of fatty alcohols.
When a relatively low degree of ethoxylation, i.e. one to four moles, is desired, an undesirably broad molecular weight product distribution is obtained. The broad distribution is due to the similar basicity of the alcohol and ethoxylate. Additive ethoxylation proceeds at the expense of ethoxylation of alcohol. Consequently, low mole ethoxylate products typically have relatively large amounts of unreacted alcohol. Residual alcohol in the product presents odor problems and reduces the smoke point. A low smoke point is especially problematic during the spray-drying of powdered detergents containing ethoxylated nonionic surfactants, when a low smoke point may result in undesirable volatilization of the surfactants.
In addition to higher smoke points and lower odor, ethoxylates of narrow molecular weight distribution have performance advantages over ethoxylates of broad molecular weight distribution. They include the following: (i) lower viscosity and pour point for easier handling; (ii) higher cloud point; (iii) higher initial foaming and less foam stability; (iv) better wetting properties; (v) increased interfacial surface tension reduction compared to paraffin; and (vi) higher surface tension than conventional ethoxylates.
Various processes have been proposed in the base catalysis art to reduce the molecular weight distribution of alkoxylates. Such art is seen, for example, in U.S. Pat. Nos. 3,471,411; 3,969,417; 4,112,231; 4,210,764; 4,223,163; 4,223,164; 4,239,917; 4,278,820; 4,302,613; 4,306,093; 4,360,698; 4,396,779; 4,453,022; 4,465,877; 4,453,023; 4,456,773; 4,456,697; 4,721,817; 4,727,199; 4,754,075; 4,764,567; 4,775,653; 4,885,009; 4,832,321 and 5,220,046, which are incorporated herein by reference. However, the art has to date failed to propose a base catalysis process for making alkoxylates of sufficiently narrow molecular weight distribution.
One means for making alkoxylates of narrower molecular weight distribution is to employ acid catalysis to effect polymerization. Acid catalysis has been generally disfavored, however, in the art because of the formation of relatively high levels of undesirable by-products. For instance, polyoxyethylene is formed by competing dehydration reactions and dioxane and 2-methyldioxolane are formed by competing cyclization reactions.
Processes for making alkoxylates of narrow molecular weight range with catalysts of rare earth metals have been proposed. U.S. Pat. Nos. 5,057,627 and 5,057,628 disclose processes for making alkoxylates of narrow molecular weight range with catalysts of monometallic salts of rare earth elements. U.S. Pat. No. 5,059,719 discloses processes for making alkoxylates with basic rare earth compounds such as rare earth alkoxides. U.S. Pat. No. 5,641,853 discloses the polymerization of oxetanes, 1,3-dioxolanes, 1,3,5-trioxanes and tetrahydrofurans to linear polyethers with metal compounds such as rare earth triflates and perfluoroalkylsulfonates. U.S. Pat. No. 5,677,412 discloses the polymerization of cyclic ethers and organic isocyanates catalyzed by metal compounds such as transition metal and rare earth perfluoroalkylsulfonates and rare earth triflates. EP 855417 discloses a process for making ethoxylates from a hydrogen labile compound and a alkyleneoxide using perfluoroalkylsulfonate salts of transition metals or rare earths. Rare earth triflates are preferred. Rare earth catalysts have afforded the production of ethoxylates of narrower molecular weight distribution with a lower degrees of residual active hydrogen organic starting material, i.e. an alcohol.
In view of the foregoing, it would be desirable to have a new and effective process for making alkoxylates of still narrower molecular weight distribution. Further, it would be desirable to have a process which afforded a still lower degree of residual active hydrogen organic starting material. Still further, it would be desirable to have a process which afforded a lower degree of undesirable by-products.
It is an object of the present invention to produce alkoxylated organic compounds of narrow molecular weight distribution.
It is a further object of the present invention to produce alkoxylated organic compounds and leave relatively low proportions of residual starting materials.
It is a further object of the present invention to produce alkoxylated organic compounds with relatively low proportions of undesirable by-products.
It is still a further object of the present invention to provide a process for making alkoxylates of active hydrogen organic compounds. The process requires (a) providing an active hydrogen organic compound having an alkyl group of about 8 to about 20 carbon atoms and (b) alkoxylating the organic compound in the presence of a catalytically effective amount of a rare earth triflimide of the following formula:
R1R2R3X
wherein X is selected from the group of lanthanides, consisting more specifically of neodymium, ytterbium, gadolinium, lanthanum, cerium, praseodymium, samarium, europium, terbium, dysprosium, erbium, thulium, and lutetium. R1, R2, and R3 are each independently a triflimide group of the following formula:
N(SO2Z)2
wherein Z is CnF2n+1. C is a carbon atom and F is a fluorine atom. xe2x80x9cnxe2x80x9d is an integer from 1 to 15. Z is preferably CF3.
In the process of the present invention, it was found unexpected that alkoxylates of narrow molecular weight distribution could be prepared using a catalyst of rare earth triflimides. It was also surprising that such alkoxylates could be prepared leaving a relatively low degrees of residual active hydrogen organic starting material and undesirable by-products.
The rare earth triflimide catalysts useful in the present invention are of the following formula:
R1R2R3X
wherein X is selected from the group of lanthanides, consisting more specifically of neodymium, ytterbium, gadolinium, lanthanum, cerium, praseodymium, samarium, europium, terbium, dysprosium, erbium, thulium, and lutetium. R1, R2, and R3 are each independently a triflimide group of the following formula:
N(SO2Z)2
wherein Z is CnF2n+1. C is a carbon atom and F is a fluorine atom. xe2x80x9cnxe2x80x9d is an integer from 1 to 15. Z is preferably CF3.
Preferred rare earth triflimides are those of neodymium, ytterbium and gadolinium. Corresponding formulas for the preferred triflimides are Nd[N(SO2CF3)2]3, Yb[N(SO2CF3)2]3 and Gd[N(SO2CF3)2]3.
Rare earth triflimides can be prepared by reaction of rare earth oxides and bistrifluoromethane sulfonamide acid. For instance, the preparation of lanthanum triflimides is shown in the following reactions:
xe2x80x83Ln2O3+6(CF3SO2)2NHxe2x86x922Ln[N(SO2CF3)2]3+3H2O
or
Ln2(CO3)3+6(CF3SO2)2NHxe2x86x922Ln[N(SO2CF3)2]3+3CO2
The rare earth triflimide catalyst is employed in a catalytically effective amount. Preferably, the catalysts are employed at about 1.0xc3x9710xe2x88x925 M to about 1.0xc3x9710xe2x88x921 M based on the organic compound.
The active hydrogen organic compound employed in the present process has 1 to 22 carbon atoms. Useful active hydrogen organic compounds include alcohols, amines, mercaptans and amides. Preferred compounds are hydrophobic and have from 8 to 22 carbon atoms. Preferred compounds are also hydroxylated. Preferred compounds include fatty alcohols. Fatty alcohols can be obtained from natural sources such as fats and oils or may be derived synthetically from petroleum. Natural alcohols are prepared from natural fatty acids derived from coconut oil, palm kernel oil, palm oil, tallow, soya, sperm oils and the like. Useful fatty alcohols include octanol, nonanol, decanol, dodecanol, palmityl alcohol, octadecanol, eicosanol, behenyl alcohol, and stearyl alcohol and mixtures or blends of the foregoing. A most preferred fatty alcohol is dodecanol. Unsaturated alcohols such as oleoyl, linoleic and linolenic alcohols are also useful. Synthetic alcohols may be prepared using the oxo (hydroformylation of carbon monoxide and hydrogen) or the Ziegler (ethylene and triethylaluminum) processes. Typical alcohols are oxodecyl, oxotridecyl, oxotetradecyl alcohol. Useful alcohols include Neodol 23, 25 and 91 (Shell Corp.). Aromatic alcohols are also useful. Typical aromatic alcohols are nonylphenol, octylphenol, diisobutylphenol, dodecylphenol and dinonylphenol. Useful low molecular weight alcohols include methanol, ethanol, propanol, butanol and other C1 to C7 alcohols.
Alkoxylation is carried out by contacting the active hydrogen organic compound with an alkylene oxide under catalytically effective conditions. The reaction is carried out in the presence of the rare earth triflimides, which are Lewis acids. The alkoxylation reaction can be carried out in temperature conditions from about 20xc2x0 C. to 200xc2x0 C.
Alkoxylation include the reactions of ethoxylation, propoxylation, and butoxylation. Alkoxylation reactions involving adducts of higher numbers of carbons are possible and within the scope of the invention. Useful alkylene oxide reactants include but are not limited to ethylene oxide, propylene oxide, butylene oxide and cyclohexene oxide. An important reaction industrially is ethoxylation, which typically involves the addition of ethylene oxide to a organic compound. More specifically, an important reaction is the ethoxylation of dodecanol.
The present process affords the production of product having relatively narrow molecular weight distribution. Although not bound by any particular range or level of distribution, degrees of narrowing up to about 95% are possible. Preferred degrees of narrowing range from about 80 to about 95%. Degree of narrowing are determined according to the formula and method set forth below.
The present process affords advantages over conventional base catalysis of the prior art. The present process yields alkoxylated product of considerably narrower molecular weight distribution than that produced by conventional base catalysis using potassium or sodium hydroxide. Further, the present process leaves a lower residual content of active hydrogen organic starting material, i.e. fatty alcohols, than conventional base catalysis. Further, the present process can be effected at a lower operating temperatures than with conventional base catalysis. Still further, the present process can be effected with about a tenth of the amount of catalyst normally employed in conventional base catalysis.
The catalyst can be used as is or can be supported on a mineral charge such as silica, alumno, titanium dioxide and the like. The catalyst can be left in the final product or be recycled after proper treatment.
The following are non-limiting examples of the present invention. All percentages are by weight unless indicated otherwise.